The overall long-term objective of our studies is to elucidate the molecular mechanisms involved in zinc homeostasis in mammals. Herein, we propose to study the rare, autosomal recessive trait, acrodermatitis enteropathic (AE). AE results for the inability to absorb significant dietary zinc, and a candidate gene mutated in human patients with AE was just identified. This gene encodes a member of the ZIP gene superfamily of metal transporters and was named hZIP4. We will test the hypothesis that this putative zinc transporter plays a central physiological role in zinc homeostasis using the mouse model. No mouse models for AE exist and essentially nothing is known about the regulation and functions of ZIP4. In preliminary studies, we have cloned the mouse ZIP4 gene and cDNA, determined that it is highly expressed in the intestinal tract, and demonstrated that mZIP4 mRNA is dramatically up-regulated during periods of dietary zinc deficiency. Therefore, the specific aims of this proposal are to: 1) Delineate the metal transport properties of native and AE mutants of mZIP4; 2) elucidate the mechanisms of metallo-regulation of mZIP4 expression; and 3) determine the affects of targeted mutation of the mZIP4 gene on zinc homeostasis in the mouse. This project represents a collaborative effort between the laboratories of Drs. Andrews, Eide, and Peterson. The P.I., Dr. Andrews is an expert in mammalian embryonic development and zinc deficiency, and in metalloregulation of gene expression. The Co-I., Dr. Eide is an expert and leader in the field of ZIP transporter function and regulation, and Co-I., Dr. Peterson is an expert in globin locus regulation and mouse knockout strategies.